If we applied a link eg. on:
```
<span>hello <b>world</b></span>
```
The system actually gets the "label": hello worldworld because there is
3 nodes:
text node: hello
element node: `<b>world</b>`
text node: world
Also since "hello worldworld" is different than "hello world",
instead of just keeping existing nodes and adding the link, the system
would replace the selected range by:
`<span><a>hello worldworld</a></span>'
instead of:
`<span><a>hello </a><b><a>world</a></b></span>`
This commit ignores element nodes when creating a new link, since when
getting the label of the link from the selection, only the text nodes
insides the element nodes have any interest.
There was a second issue because if we had:
```
<i><a href="hello">world</a></i>!
```
and tried to put a link over "world!", the code would decide: "world" is
inside a link so we will just update that link.
Thus we would get:
```
<i><a href="hello">world!</a></i>!
```
instead of:
```
<i><a href="hello">world</a></i><a href="hello">!</a>
```
opw-1848351
closes#25187